1. Field of the Invention
This invention relates to improved footwear for athletes, of the type containing an insert at least in the heel region, the insert comprising an airtight flexible plastics casing enclosing a series of interconnected elastically deformable bodies.
2. Discussion of Background
It is well known that athletic footwear must provide a stable support region which at the same time is comfortable for the foot and hence for the athlete's body, which is subjected to most various types of stress. To solve the problem of comfort with stable support, while also achieving a certain counterthrust effect, i.e. a partial recovery of the thrust as the footwear separates from the ground plus absorption of the impact against the ground, solutions of the type described in the preceding paragraph have been proposed.
The known-art inserts positioned in the footwear heel act primarily as a complex spring, so that after the impact of the footwear against the ground and the simultaneous damping effect, there is partial restitution of the energy absorbed by the insert on impact. Although the known inserts offer comfort, stability and adequate damping and energy recovery through a certain range of loading and impact velocity, they can prove partially unsatisfactory outside these ranges. For example, footwear provided with the insert in question can satisfy the requirements of slow movement but not of fast movement, whereas an insert designed for fast movement could prove too rigid for slow movement. In addition to this, for equal footwear size the weight of the wearer can vary within extremely wide limits, so that the same insert can prove either excessively rigid or excessively yielding.